prosthesis for inserting into a damaged intervertebral disc. The prosthesis has an elongated tubular main prosthesis body with a length to fit laterally from one side of a disc to the other at its mid-plane. The main prosthesis body is composed of two parts transversely oriented and has a vertical height deliberately greater than the height of normal disc space. Heads having a vertical height greater than the vertical height of the main prosthesis body are mounted on the ends of the main prosthesis body.
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1. A spinal prosthesis system for inserting laterally from one side only into an intervertebral disc space between two adjacent vertebrae comprising: an elongated, rigid load-bearing main prosthesis body having opposed ends and having a vertical height deliberately greater than the height of normal disc space of an intervertebral disc into which it is to be inserted and having opposed elongated surfaces configured to contact and distract the upper and lower adjacent vertebrae, said main prosthesis body sized to fit laterally from one side of a disc to the other at its mid-plane and sized to maintain the space between the adjacent vertebrae distracted; said main prosthesis body having a longitudinally extending through passageway open at its ends; a proximal cap directly mounted in fixed relation on one end of the main prosthesis body in a position to lie outside the normal disc space of an intervertebral disc and sized to have a vertical height greater than the vertical height of the main prosthesis body to bear against the sides of the adjacent vertebrae and defining an opening in axial alignment with one end of said passageway; and a distal cap removably mounted on the other end of the main prosthesis body in a position to lie outside the normal disc space of an intervertebral disc and sized to have a vertical height greater than the vertical height of the main prosthesis body to bear against the sides of the adjacent vertebrae, and defining an opening in axial alignment with the other end of said passageway; and an elongated, locking member received in said passageway and having a first end releasably engaging the opening in said proximal cap to prevent relative rotational movement therebetween and a second end releasablv engaging the opening of said distal cap to prevent relative longitudinal movement therebetween; wherein said rigid load-bearing main prosthesis body being composed of two parts, a first longitudinally extending radial inner part and a second longitudinally extending radial outer part, said parts being superimposed and mounted together radially.
2. The spinal prosthesis system of
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10. The spinal prosthesis system of
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This application is a continuation-in-part of application Ser. No. 12/233,107 filed Sep. 18, 2008 now U.S. Pat. No. 8,187,333 and the benefits of 35 USC §120 are claimed.
1. Field of the Invention
The invention relates to prostheses for intervertebral discs that are easily and quickly implantable, a method for easily and quickly implanting and a method for easily and quickly explanting.
2. Description of the Related Art
Intervertebral discs (or more simply “discs”) lie between adjacent vertebrae in the spine. Each disc forms a cartilaginous joint to allow slight movement of the vertebrae and acts as a ligament to hold the vertebrae together.
Discs include an outer annulus fibrosus, which surrounds the inner nucleus pulposus. The annulus fibrosus includes several layers of fibrocartilage. The nucleus pulposus contains loose fibers suspended in a mucoprotein gel, which has the consistency of semi-hard and slightly fibrous connective tissue or cartilage. The nucleus of the disc acts as a shock absorber for distributing pressure evenly across the disc and for absorbing the impact of bending and twisting of the spine while keeping the two abutting vertebrae separated. When one develops a prolapsed disc, the nucleus pulposus is forced out resulting in pressure being put on nerves located near the disc. This can cause severe pain and neurological problems.
There is one disc between each pair of adjacent vertebrae, except between the first and second cervical vertebrae. The atlas is the first cervical (neck) vertebra which is just under the head. The axis is the second cervical vertebra. The axis acts as a post around which the atlas can rotate, allowing the neck to rotate. There are a total of twenty-three discs in the spine. The discs are most commonly identified by specifying the particular vertebrae they separate. For example, the disc between the fifth and sixth cervical vertebrae is designated “C5-6”.
As people age, the intervertebral discs degenerate. Two typical processes occur. The nucleus pulposus dehydrates and flattens, which limits its ability to absorb shock. The annulus fibrosus gets weaker with age and develops fissures or tears. As the discs dehydrate, the disc spaces change and the space for adjacent nerves narrows. In the neural foramens, this is called foraminal stenosis; in the spinal canal, this is called central stenosis. The discs bulge outward, and bone spurs (osteophytes) form along the bulging disc surfaces that also pinch adjacent nerves (spinal cord, cauda equina, and nerve roots). A flattening disc causes stress to the posterior elements of the spine and also the facet joints. Although these conditions may not cause pain in some people, others experience acute and chronic pain.
Pain, weakness, and numbness due to pinching of the nerves protruding from the spine are called radiculopathy or radiculitis. Pain, weakness, and numbness due to pinching of the nerves inside the spinal canal is known as radiculopathy, radiculitis, cauda equina syndrome or myelopathy, depending on the level of the spine and the type of symptoms.
When the annulus fibrosus tears due to an injury or the degenerative process, the nucleus pulposus can begin to extrude through the tear. This is called disc herniation. Near the posterior aspect of each disc, at each vertebral level or segment, a pair of major spinal nerves extends outward, to different organs, tissues, extremities, etc. Herniated discs often press against these nerves (pinched nerve) and the spinal cord causing neurologic dysfunction including sensory and/or motor loss and/or pain.
Herniated disc, ruptured disc, bulging disc, degenerative disc, protrusion, extrusion, all refer to related processes and are used more-or-less synonymously, depending on the medical professional. There is no true standard nomenclature, and the various terms mean different things to different people. Also, the degree to which there is pressure on the nerves (e.g. stenosis, pinching, nerve root elevation, cord compression, effacement, and many other descriptions) also varies.
To treat impaired discs, many techniques and devices have been used. Some treatments remove, dissolve, or vaporize disc material (e.g. chymopapain injection, microsurgical discectomy, nucleotomy, laser discectomy, radiofrequency ablation, and others). Other treatments fuse the disc (e.g. cages, screws, bone grafts, bone morphogenic protein, and others). Disc removal procedures remove the disc. Fusion procedures result in loss of motion of the disc and juxtaposed vertebrae.
Accordingly, there is a need for an implantable prosthesis that treats the conditions noted above in a more efficacious manner to restore to a damaged disc area the original natural body motion function. This need is met by the implantable prosthesis of the invention that is easily and quickly implantable. Using the prosthesis of the present invention, adjacent and abutting vertebrae adjacent to the damaged disc area will be able to move relative to each other in a more natural way. The prosthesis of the invention enables motion of the adjacent and abutting vertebrae the same as the natural motion of healthy adjacent vertebrae of the spine. In particular, the prosthesis that can be easily and quickly positioned relative to a normal axis of rotation, and will function to support or restore normal vertebral movement. The prosthesis of the invention is implanted into a damaged intervertebral disc in a simple and direct manner. The prosthesis of the invention affords “dynamic stabilization” and “motion preservation”.
It is accordingly an object of the invention to provide a novel intervertebral disc prosthesis that is quickly and easily implantable, a method for quickly and easily implanting and a method for quickly and easily explanting the novel intervertebral disc prosthesis in the event the indications are such that removal of the prosthesis is desirable. The prosthesis of the present invention overcomes the above-mentioned disadvantages of known prosthesis of this general type. The foregoing object of the invention is accomplished by the novel disc prosthesis of the present invention, which consists of an elongated metal, ceramic or hard plastic, biocompatible implant that has a shape suitable for insertion into the nucleus pulposus of a degenerative intervertebral disc to restore normal body motion with respect to the adjacent and abutting vertebrae. The implant is placed through the disc annulus laterally and extends from one side to the other and has caps or heads on its ends that bear against the adjacent vertebrae, so that it is held in position. Defining features of the disc prosthesis are that it is (1) held in place by the end caps and (2) has a main prosthesis body that can potentially be modified in any conceivable way to distract the interspace sufficiently to provide decompression and improvement of alignment. Alternatively, it can be used as a spinal fusion device. The disc prosthesis primarily is meant to allow for natural or near natural motion of the spine. When implanted, the disc prosthesis has a height slightly greater than the normal disc spatial opening and thus, sufficiently distracts the adjacent and abutting vertebrae. It can be used for cervical, thoracic or lumbar degenerative discs. The disc prosthesis is purposefully designed to be larger than the disc interspace in order to distract the abutting two vertebrae apart from one another sufficiently to change the shape of the spine. Distracting adjacent vertebrae apart from one another causes (1) opening of the neural foramens which thereby produces decompression of the (pinched) nerve roots as they exit the neural foramens, (2) decompression of the spinal cord and/or nerve roots in the central spinal canal via unbuckling of the ligamentum flavum, and (3) re-alignment of scoliosis by equalizing the intervertebral disc height on both sides.
In accordance with the invention, in its preferred form, the novel disc prosthesis is assembled from three members, namely, (i) an elongated main prosthesis body of a preselected shape having a height or vertical thickness greater than the normal disc height, and having at one end a proximal cap (integrally formed or attached) having a height greater than the body height, (ii) a distal cap having a height greater than the body height is mounted on the other end of the main prosthesis body and (iii) a locking member coacting with the other two members that prevents rotary motion and holds the assembly together. The prosthesis can include quickly attachable and detachable acting mutually coacting elements to lock the prosthesis axially to prevent disassembly except when desired. The assembled novel prosthesis is implanted laterally from one side (the proximal side) into a hole drilled into the disc space and spans the intervertebral disc space completely from side-to-side so that the distal and proximal caps contact opposed lateral sides of the disc and the adjacent, abutting vertebrae. As the height of the main prosthesis body is greater than the normal disc height, when implanted, the abutting vertebrae are slightly distracted and placed under slight tension. The main prosthesis body has a length at least as great as the disc lateral width. To implant, an annulotomy track or annulotomy hole is drilled laterally through the disc in the region of its central vertical plane using minimally invasive surgical techniques, such as, arthroscopic techniques, i.e. the hole is drilled from one side of the disc only laterally to the other side. The final section of the hole is completed by a punch to create a lateral through hole. Using a suitable set of instruments, which in the preferred embodiment will utilize a series of distracting rods of increasing diameter to enlarge the through hole, the assembled prosthesis can thereby be quickly and easily forced through the hole from the proximal side of the disc laterally to the distal side of the disc. During this process, the distal cap distracts significantly the adjacent, abutting vertebrae. When the distal cap has passed through and emerges out the distal lateral side, the adjacent, abutting vertebrae retract slightly to contact the main prosthesis body. However, because the height of the main body of the prosthesis is greater than the height of the disc space, the adjacent, abutting vertebrae are still slightly distracted and under slight tension. Due to the shape of the main prosthesis body, the contact between the main prosthesis body and the adjacent, abutting vertebrae can be a line or point contact, or an areal contact that is very narrow in a direction normal to the longitudinal axis of the prosthesis if the prosthesis is essentially circular in cross section and the distal and proximal caps slightly contact opposed lateral sides of the disc and the adjacent, abutting vertebrae enabling a rotation of the implant about its longitudinal axis. However, for an elliptical and an inflatable prosthesis the areal contact would have a defined width and a large and variable areal contact, respectively. To quickly and easily explant the prosthesis, special tools are used to first unlock the prosthesis by removal of the locking member, then to remove the distal cap from the main prosthesis body, and finally to pull the main prosthesis body out from the proximal side of the lateral hole in the disc. The distal head now separate from the rest of the implant remains in the body.
The prosthesis can take other forms, such as, it may consist of a single rod or tube with integral or detachable heads, or only one head is detachable. The rod can be in two parts that are connected together axially, by, for example, by threading, or splines, or any other connecting elements that hold the two parts together. The prosthesis can take a form that does or does not include the locking member described above. The rod can also be in two parts radially. The inner part is cylindrical and circular in cross section and the outer part can assume any shape.
To begin an implant procedure, a tube is inserted or a working channel is created using a lateral approach to the disc at its lateral mid-plane. A skin incision is made to only one side of the intervertebral disc, i.e. the prosthesis is placed from one side of the patient's body only. The tube or cannula is placed against the lateral side of the intervertebral disc in which the prosthesis is to be inserted. The tube provides a working space in which the prosthesis and tools are delivered to the intervertebral disc. A minimally-invasive technique may be accomplished in a known manner, such as with a tube retractor. A drill is initially delivered via the tube or working channel to drill a guide track and a nearly through-hole in the intervertebral disc. This procedure is known as an annulotomy. The annulotomy defines a track laterally through the intervertebral disc. The final opening on the distal side of the disc can be made using a punch or awl. Now the lateral through-hole is completed and has a proximal opening and a distal opening. The location of the lateral hole is at its lateral mid-plane or just posterior to this point, the slightly more posterior location being close to the natural axis of rotation of the spinal segment. Preferably, the location is from a location near the lateral mid-plane of the disc to a location at a parallel plane not more than one-half the distance from the lateral mid-plane of the disc to the posterior of the disc.
The next step of the method involves forcing the assembled prosthesis distal cap first into and through the hole along the annulotomy track from the proximal side of the disc to the distal side of the disc whereupon it emerges. To accomplish this a series of distracting rods of increasing diameter is used to enlarge the through-hole, which then allows the assembled prosthesis to be quickly and easily forced therethrough. This step involves dilating up the through-hole prior to placing the prosthesis. The dilators (the series of distracting rods of increasing diameter) would also be used to gauge the diameter size of the prosthesis that would be required for the particular disc. A set of dilators for the task can be color coded for increasing diameters from 6 mm to 14 mm, in 2 mm increments. As noted, because the distal cap is of a greater height than the prosthesis body and the disc, the adjacent, abutting vertebrae are distracted during this step. With the prosthesis fully implanted, both the distal and proximal caps lie outside the disc and bear laterally against the proximal and distal sides of the disc and also bear against the adjacent, abutting vertebrae.
The present invention discloses a prosthesis for inserting into an intervertebral disc having a normal disc height, a normal disc width, and a disc annular wall, comprising:
The novel prosthesis for inserting into an intervertebral disc has a disc height, a disc width, and a disc annular wall can comprise:
The prosthesis as noted above can have its main prosthesis body cylindrical in shape, and the main prosthesis body can be one of right cylindrical, elliptical and prolate spheroid in shape. The main prosthesis body can be made of any of a number of different materials, such as, hydrophilic expandable material, polymer, metal, PEEK, ceramic, woven fabric, non-woven fabric, rubber, silastic, acrylic, concentric layers of materials, alternating layers of materials, tempered glass or layered tempered glass, certain metals and alloys, certain synthetic polymers and other materials found to be biocompatible with the human body and combinations thereof. The heads can be made of any of the listed materials. The heads can be disc shaped or of any other shape. The second or distal head can be attached to the main prosthesis body by a joint that requires relative rotation to detach. The second or distal head can be non-detachable and fixed to the main prosthesis body or the second or distal head can be connected by a joint that articulates. The openings in the heads can be non-circular shaped. The opening in the second or distal head can be polygonal shaped, for example, hex shaped. The locking member can have a complementary shaped end that fit into the opening in the second or distal head. As noted above, each component or piece of the prosthesis can be made of one or more of the listed materials in combination.
The locking member of the prosthesis and the second or distal head can have quick detachable mutually coacting elements that prevent longitudinal movement of the locking member relative to the second head. The quick detachable mutually coacting elements can comprise any known set of coacting elements, such as, for example, a bayonet connection or a detent connection. A preferred set of coacting elements is a series of projecting flat bars peripherally arranged in a polygonal shape, preferably a hex shape, at the end of the locking member, each bar having peripherally extending bump coacting with a shoulder defined in the hex opening of the second or distal member. The first and second heads can have flat surfaces facing inwardly toward the main prosthesis body that can bear against the annular wall and the abutting vertebrae when the prosthesis is implanted in the disc, but without too much pressure so that relative rotation is not impeded. The opening in said first or proximal head can be hex shaped and the locking member can have a hex shaped end that fits into the hex opening of the first head in a recessed manner. The hex shaped openings and the coacting hex shaped elements can have other shapes, such as, square, diamond, cruciform, triangular, octagonal or any other polygonal or non-circular shape.
In a further embodiment the second or distal head would not be detachable, i.e. it would be fixed to the main body, and the pieces of the prosthesis otherwise would be the same as described in shape, materials and functions. In a still further embodiment, the distal head can be mounted to the main body of the prosthesis by an articulation, such as a ball-in-socket joint, for example. In another further embodiment, the distal head has a detachable connection with the main prosthesis body. Also, in still another further embodiment the prosthesis can include a locking member to prevent unintended detachment of at least one head and the main prosthesis body. Further the main body of the prosthesis can be divided radially or transversely to its elongated axis so that a radially inner part has an outer surface circular circumference and a radially outer part that is mounted on the radially inner part and rotatable relative thereto either freely or freely limited to a predefined or preselected arc of less than 360 degrees.
An aspect of the present invention is a method for treating a person having a damaged intervertebral disc comprising the steps of:
In another aspect the invention is a method for treating a person having a damaged intervertebral disc comprising the steps of:
In a still further aspect the invention is a method for treating a person having a damaged intervertebral disc between abutting vertebrae comprising the steps of:
In yet another aspect the invention is a method for treating a person having a damaged intervertebral disc comprising the steps of:
The invention also contemplates a method of explanting a prosthesis implanted according to the above including the steps of:
In another embodiment, a method of explanting can include the steps of:
In further embodiments a spinal prosthesis is provided for inserting laterally from one side only into an intervertebral disc space between two adjacent vertebrae comprising: an elongated, rigid load-bearing main prosthesis body having a longitudinal axis and having opposed ends and having a vertical height deliberately greater than the height of normal disc space of an intervertebral disc into which it is to be inserted and having opposed elongated surfaces configured to contact and distract the upper and lower adjacent vertebrae, said main prosthesis body sized to fit laterally from one side of a disc to the other at its mid-plane and sized to maintain the space between the adjacent vertebrae distracted; a first cap directly mounted in fixed relation on one end of the main prosthesis body in a position to lie outside the normal disc space of an intervertebral disc and sized to have a vertical height greater than the vertical height of the main prosthesis body to bear against the sides of the adjacent vertebrae; and a second cap mounted on the other end of the main prosthesis body in a position to lie outside the normal disc space of an intervertebral disc and sized to have a vertical height greater than the vertical height of the main prosthesis body to bear against the sides of the adjacent vertebrae; wherein the main prosthesis body is composed of an inner part and a transversely oriented outer part.
In the prosthesis according to the above the inner part of said main prosthesis body is cylindrical in shape and circular in cross section. Also, the transversely oriented outer part of the main prosthesis body can be nested on the inner part and coaxial and relatively rotatable with respect thereto. Alternatively, the transversely oriented outer part of the main prosthesis body can be nested on the inner part and non-rotatable relative thereto. Also, the transversely oriented outer part of the main prosthesis body can be inflatable.
Further, in the spinal prosthesis according to the above, the inner part of said main prosthesis body can have a longitudinally extending through passageway open at its ends with the proximal cap defining an opening in axial alignment with one end of the passageway, and the distal cap defining an opening in axial alignment with the other end of the passageway with an elongated, locking member being received in the passageway that has a first end engaging the opening in the proximal cap and a second end engaging the opening of the distal cap to prevent relative movement.
In the prosthesis according to the above the transversely oriented outer part of said main prosthesis body can be cylindrical in shape, and can be one of right cylindrical, elliptical, prolate spheroid, longitudinally undulating, a longitudinal sawtooth shape, a defined irregular shape and a shape designed to change over time within the body. The adjacent surfaces of two parts of the main prosthesis body define one of splines, keyways and interlocking elements. Further, the main prosthesis body is made from material biocompatible with the human body. Also, the caps are shaped and sized to be of a height from about 110% to about 250% of the height of the main prosthesis body. Still further, the distal cap can be attached to the main prosthesis body by a joint that requires relative rotation to detach. The openings in the caps can be non-circular shaped. The opening in the distal cap can be hex shaped. The caps can have flat surfaces facing inwardly toward the main prosthesis body.
In the prosthesis employing a locking member, the locking member can have a non-circular shaped end that is received in the non-circular shaped opening in the distal cap. The locking member and the distal cap can define quick-detachable mutually-coacting elements that prevent longitudinal movement of the locking member relative to the distal cap. The quick detachable mutually coacting elements can comprise projecting flat bars peripherally arranged in a non-circular shape at the second end of the locking member with each bar having a peripherally extending bump to coact with a shoulder defined in the non-circular shaped opening of the distal cap. The opening in the first (proximal) cap can be non-circular shaped. Further, the locking member can be non-circular shaped at its first end and fits into a non-circular shaped opening of the first (proximal) cap in a recessed manner.
In a further embodiment the prosthesis according to the above can be arranged with the transversely oriented outer part inflatable, and a conduit defined in the inner part that communicates with an opening in the transversely oriented outer part at one end and with an opening in the inner part at its other end, and a one-way check valve is located in the conduit to enable fluid to flow into but not out of the transversely oriented outer part. In this embodiment a tool is inserted into the conduit to upset the check valve to enable flow out of the inflated transversely oriented outer part.
Other features and advantages of the invention will be evident from the following detailed description when taken in conjunction with the appended drawings. Changes may be made therein, as will be evident to those of skill in the art, without departing from the spirit, scope and teachings herein of the invention and its range of equivalents as expressed in the claims.
Referring now to the figures of the drawing in detail and first, particularly to
The prosthesis 10, in assembled form, as shown for example in
To begin an implant procedure, a tube 52 is inserted or a working channel is created using a lateral approach to the disc 1 at its lateral vertical mid-plane. The terms proximal and distal reference to how the prosthesis is inserted into the intervertebral disc 1. A skin incision is made to only one side of the intervertebral disc 1. The prosthesis 10 is placed from one side of the patient's body only. The tube or cannula 52 is placed in a known manner against the lateral side of the intervertebral disc 1 in which the prosthesis 10 is to be inserted. The tube 52 provides in a well-known manner a working space in which the prosthesis 10 and tools are delivered to the intervertebral disc 1. A minimally-invasive technique may be accomplished with a tube retractor. A drill 50 is initially delivered via the tube or working channel 52 to drill a guide track and nearly through hole in the intervertebral disc 1. This procedure is known as an annulotomy. The annulotomy defines a track 56 laterally through the intervertebral disc 1. The final opening on the distal side of the disc is made using a punch 58. Now the lateral through-hole 56 is completed and has a proximal opening and a distal opening. The next step would be to
The next step of the method involves quickly and easily forcing the assembled prosthesis distal cap 22 first into and through the hole 56 along the annulotomy track from the proximal side of the disc 1 to the distal side of the disc 1 whereupon it emerges. To accomplish this a series of distracting rods of increasing diameter is used to enlarge the through-hole, which then allows the assembled prosthesis to be quickly and easily forced therethrough. This step involves dilating up the through-hole prior to placing the prosthesis. The dilators (the series of distracting rods of increasing diameter) would also be used to gauge the diameter size of the prosthesis that would be required for the particular disc. A set of prototype dilators for the task can be color coded for increasing diameters from 6 mm to 14 mm, in 2 mm increments. As noted, as the distal cap is of a greater height than the body 14 of the prosthesis and the disc 1. The caps are sized to be from about 110% to 250% of the size of the main prosthesis body. Accordingly, the adjacent, abutting vertebrae are significantly distracted during this step. With the prosthesis fully implanted, both the distal and proximal caps 22 and 16 are outside the disc 1 bearing laterally against the distal and proximal sides of the disc 1 and also bearing against the adjacent, abutting vertebrae. By a suitable instrument, the assembled prosthesis 10 is forced quickly and easily through the hole 56 from the proximal side of the disc 1 laterally to the distal side of the disc 1. During this process, the distal cap 22 distracts the adjacent, abutting vertebrae. When the distal cap 22 has passed through and emerged out the distal lateral side, the vertebrae retract slightly to contact the main prosthesis body 14. As the main body 14 of the prosthesis 10 is slightly greater in height than the normal disc space, the adjacent, abutting vertebrae are still slightly distracted and under slight tension. To explant the prosthesis 10, special tools are used to first quickly and easily to pull the hex locking member 30, and then, special tools are used to quickly and easily remove or detach the distal cap 22 and pull out the main prosthesis body 12. All this activity takes place quickly and easily from the proximal side of the lateral hole in the disc 1. Explanting will be described in detail hereinafter.
Due to the shape of the main prosthesis body, the contact between the main prosthesis body and the abutting vertebrae surfaces is a line or point contact or an areal contact of very narrow width in a direction normal to the longitudinal axis of the prosthesis 10. The width of the areal contact is limited so that the prosthesis will not restrict normal motion of the adjacent, abutting vertebrae. The shape of the main prosthesis body 12 is preferably cylindrical having a cross section of one of a circle or an ellipse. An elliptical shape is shown in
Although the prosthesis is shown in
Either or both of the parts 14a and 14b may be made of any or combinations of a number of different materials such as hydrophilic expandable material, polymer, hydrogels, metal, PEEK, ceramic, woven fabric, non-woven fabric, rubber, silastic, acrylic, silicone, Teflon, PEEK-optima, Motis®, Endolign®, polyester, PTFE, polyethylene concentric layers of materials, alternating layers of materials such as laminated tempered glass product, made to any shape, alternating layers of plastic, metal, rubber, ceramic, Vitrelle®, fabric, hydrogels and so forth, tempered glass or layered tempered glass, certain metals and alloys, certain synthetic polymers and other materials found to be biocompatible with the human body and combinations thereof. Any one of the main prosthesis body, detachable head, locking member and radially added pieces described herein can be made of any one or any combination of the materials listed above. In addition, materials can be added to the prosthesis by placing or mounting on the exterior of the main prosthesis body. Such materials can include a heavy canvas like material, a woven or non-woven fabric such as Gore Tex®,
In
The cross section of the main prosthesis body may be a shape other than circular, such as, a regular or irregular polygon, and even change shape from one end to the other. The outer nested piece(s) may also have a shape in cross section that is/are non-circular.
A suitable implant tool 60 is shown in
To implant, explained in more detail, the procedure is accomplished using the following steps:
To explant quickly and easily a prosthesis, two tool are required, one for removing the hex locking member 30 and one to detach the cap 22 and remove the main prosthesis body 12.
The preassembled tool assembly is placed down the tube retractor 52 and engaged into the hex opening on the implant 10 with the sheath 84 bearing on the cap 16 and the hex shape 83 inserted into the hex opening 28. The threaded end 76 of rod 70 is screwed (clockwise) into the hex locking member 30 of the prosthesis 10 to be removed. The surgeon's left hand holds handhold sheath 84 while his/her right hand screws knob 92 clockwise. Threads 85 on inside of 84 mating with threads 95 on the cylinder 94 are reverse. This forces outwardly the knob 92 (and hex tool 78 and tool 70), disengaging the hex locking member 30 from the distal head 22 of the implant 10. The whole assembly of the removal tool can now be pulled all the way out bringing with it the hex locking member 30.
Next, a second tool assembly (final tools) is prepared whose function is to detach the distal head or disc 22 and remove the main prosthesis body 12. The assembly consists of the hex tool 78 and an engagement tool 110 as shown in
The engagement tool 110 is inserted into the hex tool 78 and the assembly is placed down the tube retractor 52 with the hex shape 83 inserted into the hex opening 28 on the implant 10. The engagement tool extends completely through the main prosthesis body 12 to the far end of the distal head 22 and the hex end 114 is received in the hex opening 24 of cap 22. During insertion, the push button 122 is depressed so that the ball 134 is retracted. When in position, the button 122 is released and ball 134 projects and engages the wall of the hex opening 24 of the cap 22. The engagement tool 110 is engaged and held with the right hand by the surgeon. The surgeon then holds the hex tool 78 with the left hand and unscrews counter-clockwise (rotates in the appropriate sense to unscrew the distal cap 22 from the main prosthesis body 12) while resisting with the right hand on the engagement tool 110 (alternatively the tool 110 can be turned clockwise while resisting with the tool 78) until cap or head 22 is fully unscrewed. The tool 110 is disengaged momentarily to let the distal head 22 release/drop off. The tool 110 is reengaged within the remainder of the prosthesis which is pulled out the rest of the way. The detachment and pull out of the prosthesis is managed quickly and easily.
In
The prosthesis and each of its components can be made of any or combinations of the following materials; hydrophilic expandable material, polymer, metal, PEEK, ceramic, woven fabric, non-woven fabric, rubber, silastic, acrylic, concentric layers of materials, alternating layers of materials, tempered glass or layered tempered glass, certain metals and alloys, certain synthetic polymers and other materials found to be biocompatible with the human body and combinations thereof of these materials. The main prosthesis body 12 can be hollow and/or inflatable and filled with water, air, hydrogel, silicone rubber, acrylic, other liquid or gas under pressure, as shown in
Whereas the coupling of the cap 22 and the main prosthesis body 12 is shown by threading, other types of coupling can be used. For example, this coupling can be a bayonet type coupling for quick easy connection and decoupling. For a bayonet coupling, it is only necessary to relatively rotate the coupled parts by as little as 30 to 45 degrees.
The cross sectional shape of the body 12 can be racetrack shape with straight sides.
The implantation technique can be used also for spinal fusion, as shown by the views of
Implant 200, like the other prostheses of the present invention can be made of any suitable biocompatible material. In this regard, the present invention envisions making any of the prosthesis of a hydrophilic material. Such materials swell to a predetermined shape when exposed to liquid, such as body fluid. A hydrophilic implant could further facilitate implantation since the implant would expand to the final desired shape in vivo.
The novel disc prosthesis of the present invention consists of an elongated metal, ceramic or hard plastic, biocompatible implant that has a shape suitable for insertion into the nucleus pulposus of a degenerative intervertebral disc to restore normal body motion with respect to the adjacent and abutting vertebrae. The implant is placed through the disc annulus laterally and extends from one side to the other and has caps or heads on its ends that bear against the adjacent vertebrae, so that it is held in position. Defining features of the disc prosthesis are that it is (1) held in place by the end caps and (2) has a main prosthesis body that can potentially be modified in any conceivable way to distract sufficiently the interspace sufficiently to provide decompression and improvement of alignment. Alternatively, it can be used as a spinal fusion device. The disc prosthesis primarily is meant to allow for natural or near natural motion of the spine. When implanted, the disc prosthesis has a height slightly greater than the normal disc spatial opening and thus, sufficiently distracts the adjacent and abutting vertebrae. It can be used for cervical, thoracic or lumbar degenerative discs. The disc prosthesis is purposefully designed to be larger than the disc interspace in order to distract sufficiently the abutting two vertebrae apart from one another to change the shape of the spine. Distracting adjacent vertebrae apart from one another causes (1) opening of the neural foramens which thereby produces decompression of the (pinched) nerve roots as they exit the neural foramens, (2) decompression of the spinal cord and/or nerve roots in the central spinal canal via unbuckling of the ligamentum flavum, and (3) re-alignment of scoliosis by equalizing the intervertebral disc height on both sides.
The disc prosthesis can be modified by providing openings in the main body of the prosthesis through which an inflatable bag contained from within the main prosthesis body when inflated can expand through the openings to cause the abutting vertebrae to distract sufficiently to produce decompression of (pinched) nerve roots as they exit the neural foramens, decompression of the spinal cord and/or nerve roots in the central spinal canal via unbuckling of the ligamentum flavum, and re-alignment of scoliosis by equalizing the intervertebral disc height on both sides. This modified structure can be used for either distraction (motion preservation) or for fusion.
A system using an inflatable and deflatable prosthesis is shown in
In order to inflate the prosthesis, a prosthesis inflation tool 346 having a through-hole 341 is threaded into the tube 322 at the cap 304. Tool 346 is shown in
To deflate the prosthesis, a prosthesis deflation tool 360 is used as shown in
The more points of contact between the prosthesis and the vertebrae the less likely the implant will fracture the endplates of the abutting vertebrae. For example an inflatable implant will have a greater areal contact scattered both longitudinally and transversely, than point or line contact. Also, (1) the main prosthesis body, detachable head, locking member, and radially added pieces as described can be made of any of the noted materials or their combinations, and (2) the prostheses may have no detachable head at all, i.e. may simply be one piece, or pieces that do not come apart. Further, openings can be made in the main body of the prosthesis that enables something to be inflated from within the main prosthesis body which then expands through the openings. Further as previously noted the prosthesis of the present invention can be used for distraction (motion preservation) or for fusion. The most defining feature of the prosthesis, of course, is that it is (1) held in place by the end caps and (2) has a main prosthesis body that can potentially be modified in any conceivable way to distract the interspace sufficiently to provide decompression and improvement of alignment, or be used as a spinal fusion device.
Although the invention has been shown and described in terms of specific embodiments, changes and modifications can be made by those skilled in the art, which do not depart from the teachings herein. Such changes and modifications are deemed to fall within the purview of the appended claims.
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